The invention relates to a humidifier for producing humidified air, and particularly, although not exclusively, to a humidifier for use with a Continuous Positive Airway Pressure (CPAP) device.
A CPAP device is used in the treatment of obstructive sleep apnea syndrome, which is a disorder characterised by cycles of snoring, obstruction of the upper airway, and partial awakening during the night. In order to treat obstructive sleep apnea, a CPAP device can be used to deliver air under continuous positive pressure to the nasal passages of the patient during sleep. The positive air pressure prevents obstruction of the upper airway so that the patient is not troubled by frequent awakenings during sleep.
In order to prevent drying of the patient's airway during use of a CPAP device, it is known to pass the air through a humidifier before supplying the air to the patient. Humidification can be achieved by simply passing the air over an area of water within a humidifier so that the air absorbs moisture from the water before being delivered to the patient.
When a humidifier is used with a CPAP device, it is convenient to be able to place the CPAP device on top of the humidifier. In this case, it is desirable that the humidifier is designed so as to form a low, generally flat base for supporting the CPAP device. Such a humidifier is known as a low-profile humidifier. Because a low-profile humidifier is of low height, it is more likely to suffer from the problem of entrainment of water droplets in the output air flow to the patient. This problem arises because as the air passes through the humidifier it induces waves on the surface of the water, and water droplets are stripped from the waves by the air flow, and carried by the air flow to the outlet of the humidifier. It is also important when designing a low-profile humidifier to ensure that maximum use is made of the available water surface area. For example, there is no point in providing a large surface area of water within the humidifier if the air flow passes over only a small portion of this area.
The present invention has arisen from attempts to overcome the above difficulties, but is not limited to low-profile humidifiers, or to humidifiers for use with CPAP devices.